Glaucoma, the leading cause of preventable blindness in the United States, affects approximately 2.2 million Americans age 40 and older.
Glaucoma is known as the “silent thief” of sight because it can quietly steal your vision. More than half of the people who have glaucoma do not even realize that they have the disease, because it damages the optic nerve and causes vision loss, often without warning.
Like a cable wire, the optic nerve is responsible for carrying the images we see to the brain. The optic nerve can be damaged when the pressure within the eye increases, usually due to a build-up of a aqueous fluid within the eye. Blind spots develop within the field of vision. These blind spots usually go undetected by the person who has glaucoma, until the optic nerve has suffered significant damage and some peripheral and central vision has been lost. The damage caused by untreated glaucoma can result in irreversible blindness.
A visual field evaluation can detect glaucoma damage in its very early stages—which is another very good reason to have regular eye exams.
Types of glaucoma
- Chronic open-angle glaucoma
In the most common type of glaucoma, the drainage “angle” (where fluids in the eye drain) is open but working less efficiently, much like an air filter that gathers dust over time and eventually becomes too clogged to work properly. The inability to drain causes pressure within the eye to rise, and results in a gradual loss of side vision.
- Acute angle-closure glaucoma
This type of glaucoma occurs when the drainage angle is completely blocked, often by the eye’s iris. This prevents any fluid from draining from the eye. Pressure within the eye suddenly and dramatically rises, causing blurred vision, headaches, severe eye pain, and the appearance of halos around lights.
- Chronic angle-closure glaucoma
This more gradual and painless type of angle closure occurs most frequently in people of African or Asian descent.
- Secondary glaucoma
This type of glaucoma, which progresses in much the same way as chronic open-angle glaucoma, occurs when scar tissue blocks the drainage angle. The first symptom is loss of side vision.
- Congenital glaucoma
This birth defect affects the drainage angle and must be treated shortly after birth to prevent blindness. Symptoms include enlarged eyes, a cloudy cornea, light sensitivity, and excessive tearing.